Investment Growth Calculator
Free compound interest and investment calculator. See how your savings grow over time with compound interest and regular monthly contributions. Calculate investment returns, interest earned, and final portfolio value. Ideal for retirement planning, savings goals, and comparing interest rates.
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Yearly Investment Growth
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Monthly Investment Growth
| Date | Initial Amount | Contributions | Investment Income | Value |
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More about Investment Growth
Compound Interest
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. The formula for compound interest with monthly compounding is:
A = P(1 + r/n)^(nt)
Where A = final amount, P = initial principal, r = annual interest rate, n = compounding frequency per year, and t = number of years.
The Power of Time
A $10,000 investment at 7% annual return grows to $19,672 in 10 years, $38,697 in 20 years, and $76,123 in 30 years. The growth accelerates because interest earns interest. This is why starting early has an outsized effect on long-term results.
Monthly Contributions
Regular contributions amplify the effect of compounding. Contributing $500 per month at 7% annual return for 30 years produces a final value of approximately $610,000. Of that total, only $180,000 comes from contributions. The remaining $430,000 is from compounding returns. Over two-thirds of the final value comes from investment returns alone.
The Rule of 72
To estimate how long it takes to double your money, divide 72 by the annual return rate. At 6%, money doubles in roughly 12 years. At 8%, it doubles in about 9 years. At 10%, approximately 7.2 years.
Real vs. Nominal Returns
Nominal returns are the raw percentage gain. Real returns subtract inflation. If an investment returns 8% and inflation is 3%, the real return is approximately 5%. When planning long-term, use real returns for a more accurate projection of future purchasing power.